// app/utils/emailVerification.util.js

const crypto = require("crypto");
const emailService = require("../services/email/email.service");
const redis = require("../config/redisClient");

const EMAIL_VERIFICATION_TTL =
  Number(process.env.EMAIL_VERIFICATION_TTL_SECONDS) || 1800;

const generateEmailVerificationToken = () => {
  return crypto.randomBytes(32).toString("hex");
};

const hashEmailVerificationToken = (token) => {
  return crypto.createHash("sha256").update(token).digest("hex");
};

const createEmailVerification = async (userId) => {
  const previousKey = await redis.get(`email-verification-user:${userId}`);
  if (previousKey) await redis.del(previousKey);
  // 1. Generate raw token
  const token = generateEmailVerificationToken();

  // 2. Hash token
  const tokenHash = hashEmailVerificationToken(token);

  // 3. Create Redis key
  const redisKey = `email-verification:${tokenHash}`;

  await redis.set(redisKey, userId, "EX", EMAIL_VERIFICATION_TTL);
  await redis.set(`email-verification-user:${userId}`, redisKey, "EX", EMAIL_VERIFICATION_TTL);

  return token;
};

/**
 * Check a verification token.
 */
const verifyEmailVerificationToken = async (token) => {
  if (!token || typeof token !== "string") {
    return null;
  }

  // 1. Hash token received from user
  const tokenHash = hashEmailVerificationToken(token);

  // 2. Build same Redis key
  const redisKey = `email-verification:${tokenHash}`;

  // 3. Search Redis
  const userId = await redis.getdel(redisKey);

  if (!userId) {
    return null;
  }

  await redis.del(`email-verification-user:${userId}`);

  return {
    userId,
    redisKey,
  };
};

//send verification email to user
const sendVerificationEmail = async (email, firstName, verificationToken) => {
  const confirmationLink = `${process.env.FRONTEND_URL}/verify-email?token=${verificationToken}`;

  // Send email
  await emailService.send({
    recipient: email, templateKey: "emailVerification",
    variables: {
      customer_name: firstName,
      confirmation_link: confirmationLink,
    }, eventId: `verify-${hashEmailVerificationToken(verificationToken)}`,
  });
};

const deleteEmailVerification = async (redisKey) => {
  await redis.del(redisKey);
};

const consumeEmailVerificationToken = async (token) => {
  if (!token || typeof token !== "string") return null;
  const redisKey = `email-verification:${hashEmailVerificationToken(token)}`;
  const userId = await redis.getdel(redisKey);
  if (userId) await redis.del(`email-verification-user:${userId}`);
  return userId;
};

module.exports = {
  createEmailVerification,
  verifyEmailVerificationToken,
  sendVerificationEmail,
  deleteEmailVerification,
  consumeEmailVerificationToken,
  hashEmailVerificationToken,
};